Function readTranscriptForLoad

src/utils/sessionStoragePortable.ts:715–791

(
  filePath: string,
  fileSize: number,
)

}

export async function readTranscriptForLoad(
  filePath: string,
  fileSize: number,
): Promise<{
  boundaryStartOffset: number
  postBoundaryBuf: Buffer
  hasPreservedSegment: boolean
}> {
  const boundaryMarker = compactBoundaryMarker()
  const CHUNK_SIZE = TRANSCRIPT_READ_CHUNK_SIZE

  const s: LoadState = {
    out: {
      // Gated callers enter with fileSize > 5MB, so min(fileSize, 8MB) lands
      // in [5, 8]MB; large boundaryless sessions (24-31MB output) take 2
      // grows. Ungated callers (attribution.ts) pass small files too — the
      // min just right-sizes the initial buf, no grows.
      buf: Buffer.allocUnsafe(Math.min(fileSize, 8 * 1024 * 1024)),
      len: 0,
      // +1: finalizeOutput may insert one LF between a non-LF-terminated
      // carry and the reordered last attr-snap (crash-truncated file).
      cap: fileSize + 1,
    },
    boundaryStartOffset: 0,
    hasPreservedSegment: false,
    lastSnapSrc: null,
    lastSnapLen: 0,
    lastSnapBuf: undefined,
    bufFileOff: 0,
    carryLen: 0,
    carryBuf: undefined,
    straddleSnapCarryLen: 0,
    straddleSnapTailEnd: 0,
  }

  const chunk = Buffer.allocUnsafe(CHUNK_SIZE)
  const fd = await fsOpen(filePath, 'r')
  try {
    let filePos = 0
    while (filePos < fileSize) {
      const { bytesRead } = await fd.read(
        chunk,
        0,
        Math.min(CHUNK_SIZE, fileSize - filePos),
        filePos,
      )
      if (bytesRead === 0) break
      filePos += bytesRead

      const chunkOff = processStraddle(s, chunk, bytesRead)

      let buf: Buffer
      if (s.carryLen > 0) {
        const bufLen = s.carryLen + (bytesRead - chunkOff)
        buf = Buffer.allocUnsafe(bufLen)
        s.carryBuf!.copy(buf, 0, 0, s.carryLen)
        chunk.copy(buf, s.carryLen, chunkOff, bytesRead)
      } else {